Method of manufacturing rotating bodies for high-speed machinery.



E. F. W. ALBXANDERS ON. METHOD OF MANUFACTURING ROTATING BODIES FOR HIGHSPEED MACHINERY.

APPLICATION FILED AUG. 3, 1907.

Patented July 25, 1911 ittorne y.

n vent or Ems t FII Mdl/exanderso Witnesses:

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ERNST F. W. ALEXANDERSON, OF SGHENECTADY, NEW" YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPQRATION 016 NEW YORK.

METHOD OF MANUFACTURING ROTATING BGDIES FGR HIGH-SFEED lv'IAGLZINERY.

T 0 all whom it may concern:

Be it known that I, ERNST F. W. ALEXAN- nrnsox, a citizen of the UnitedStates, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Methods of lilanufacturing Rotating Bodies for High- Speed llachinery, of which thefollowing is a specification.

The present invention relates especially to the manufacture of wheeldisks for elastic fluid turbines but is also applicable to other bodieswhich have high rotative speeds.

One type of turbine wheel or disk with which I am familiar is made ofboiler plate with suitably supported buckets at the periphery. Thesedisks are bored centrally to receive a hub or shaft as the case may be.By calculation and experiment I have determined that the tangentialstresses in a disk of a certain size and moving at a given speed with ashaft opening therein are 2.85 times greater than the tangentialstresses in a solid disk of the same dimensions moving at the samespeed, assuming that the elastic limit of the metal is not exceeded. Acase has come to my attention where the shaft opening in a turbine diskincreased five-sixteenths of an inch after use, thereby showing theelfects of the tangential stresses in the metal. I have discovered,however, a method of manufacture whereby a disk with a shaft opening init can be made nearly as strong as a solid disk.

In carrying out the invention in one of its forms I take a disk made ofa metal which will flow when subjected to a force of a predeterminedmagnitude and bore the shaft opening, then balance it as nearly aspossible either statically or dynamically or both, and preferably, butnot necessarily, finish it roughly by turning it approximately tofinished dimensions. The disk is then rigidly mounted on an arbor andretated at such a speed that the elastic limit of the metal is exceededby such an amount as will allow the metal to flow, or in other words tocause permanent deformation to take place. The speed at which the diskis rotated considerably exceeds that at which it will run while innormal operation in a machine, but is well below the speed at which thedisk will disrupt. Running the disk at a speed which causes stressesexceed- Specification of "Letters Patent.

Application filed August 3, 1907.

Patented July 25, igll.

Serial no. 386,989.

ingthe elastic limit results in a change in the molecular arrangementand thereafter the stresses instead of being concentrated around theshaft opening will be evenly dis tributed throughout the disk. Thisuniform distribution of the stresses materially in creases the strengthof the disk and it may thereafter be rotated atspeeds above those atwhich it could have been rotated previous to the above describedtreatment, and this without injuryu After the disk has been rotated atthe speed mentioned, or in other words, at a speed suflicient to causethe metal to flow, it is turned on a boring mill or on a lathe either onthe same or on adiiferent arbor to the finished dimensions. The bucketsare then mounted on the disk, or on the disks, if two or more areemployed to make a wheel, and it or they are ready to be permanentlymounted on the shaft.

Instead of making the disk and shaft out of separate pieces and lockingthem together, they may be made integral and the benefits abovedescribed will follow. My invention may also be utilized with advantagein those constructions wherein the .web or disk and the hub are formedintegral.

In the accompanying drawings which illustrate diag ammatically bucket orother wheels made in accordance with my invention, Figure l is adiametrical section of a wheel or disk mounted 011 a shaft before it hasbeen rotated at the desired speed; Fig. 2 is a similar section of thesame disk after it has been rotated at a speed suflicient to exceed itselastic limit, the deformation being exaggerated to make it moreapparent to the eye; Fig. 3 shows the same disk finished and mounted ona shaft of the proper size; Figs. 4, 5 and 6 are face views of the disksof Figs. 1, 2 and 3.

1 indicates a shaft on which the wheel or disk 2 is mounted.

The disk is forged or cast as best suits the requirements and the shapeof the crosssection will be made such as will secure the bestdisposition of the material to withstand the stresses to which it issubjected due to rotation of the finished structure of which it may forma larger or smaller part. The cross-section illustrated is more or lessdiagrammatic in its character and would not always be followed exactlyin practice. In

manufacture, the wheel-disks or webs are partially finished andbalanced. They are then run at such speed as will produce elongation ofthe fiber of the metal and are subsequently finished to the requireddimensions. If the wheel is to be used in a turbine, the buckets arethen mounted on the disk, usually at the periphery. The results ofrunning at such speed are graphically shown in the drawing in which thedeformation is exaggerated in order to catch the eye. The arrowsindicate that in Fig. 2 the stresses, due to the high centrifugal force,exert a strain in a radial direction, while in Fig. 3 when the disk hascome to rest there are internal stresses acting in opposite directions,those near the center of the disk tending to draw the moleculesinwardly, while nearer the center of gyration the stresses actoutwardly, diminishing toward the periphery of the disk.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

l. The method of manufacturing a body intended for high rotative speedswhich consists in rotating said body at a speed sufiiciently great tocause the metal of which it is composed to flow, and finishing it to therequired dimensions.

2. As a new article of manufacture, a rotative body comprising a shaft,and a disk carried thereby that is formed of an elastic materialdeformed beyond its elastic limit so that there exist stresses tendingto resist centrifugal force when said body is rotated.

In witness whereof, I have hereunto set my hand this 2nd day of August,1907.

ERNST F. ALEXANDERSON. Witnesses BENJAMIN B. HULL, HELEN Onronn.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

